HIGH RESOLUTION OPTICAL SPECTRA OF THE DORMANT LBV STAR P Cyg

Abstract

High resolution optical spectra (R = 60 000) of the dormant LBV star P Cyg were obtained on the BTA telescope in the wavelength range \(\Delta \lambda G7 = 780\) nm. After performing a detailed identification of different types lines (photospheric absorptions, permitted and forbidden emissions, components of lines with profiles of type P Cyg), we studied the variability of their profiles and patterns of radial velocities. The average radial velocity from positions of forbidden emissions ([N II] 5754.64, [Fe II] 5261.62, [Fe II] 7155.14 and [Ni II] 7377.83 Å) is accepted as the system \({{V}_{{{\text{sys}}}}} = - 34 \pm 1.4\) km/s. About a dozen photospheric absorptions of CNO-triad ions and Si III are found, their stable position, \({{V}_{r}}({\text{abs}}) = - 73.8\) km/s, shifted relative to \({{V}_{{{\text{sys}}}}}\) at \( - 40\) km/s, indicates that these absorbtions are formed in the pseudophotosphere region. The high-excitation emissions ([O I] 5577, 6300, 6363 Å, [O III] 4959 and 5007 Å, as well as He II 4686 Å) are absent in the spectra. The radial velocity \({{V}_{r}}({\text{DIBs}}) = - 11.8\) km/s according to the position of numerous DIBs is consistent with the position of the interstellar components of the D-lines Na I and K I forming in the galactic Perseus arm. An excess of color \(E(B - V) = 0.34 \pm {{0.03}^{m}}\) and interstellar absorption \({{A}_{v}}{{ = 1.09}^{m}}\) were determined by measurements of equivalent widths of nine DIBs.